In current great-size display panels, in order to reduce deformation of the panel, a spacer is often provided between the two substrates, and generally, in order to avoid the displacement of the spacer, for example, in a liquid crystal panel, the spacer at the side of the color film substrate presses against the thin film transistor at the side of the array substrate.
As illustrated in FIG. 1, when the panel is subject to external forces, such as shocks or impacts, the spacer 4 and a passivation layer 3 in the array substrate will abrade with each other and electrostatic charges (often being positive charges) are generated, thus forming an electric field which causes charges (often being electrons) to accumulate in the channel of the TFT, resulting in conduction between the source electrode 2 and the drain electrode 1. When the gate electrode of the TFT is at a low voltage and the TFT is shut down, the source electrode 2 is disconnected from the drain electrode 1. But if the charges accumulated in the channel of the TFT are enough to conduct the source electrode 2 and the drain electrode 1, the drain electrode 1 will supply power to the pixel electrode 5, such that an unstable press spot is generated in the panel when displaying a black picture, producing defects in display of the panel.
FIG. 2 is an equivalent schematic view illustrating formation of the press spot, wherein the dashed line indicates the conduction path between the source electrode S and the drain electrode D formed due to the abrasion between the spacer and the passivation layer. When the voltage across the gate electrode G and the source electrode S is smaller than a threshold voltage, the source electrode S should be disconnected from the drain electrode D, but as illustrated in this Fig, due to effect of the accumulated charges, the source electrode S is conducted with the drain electrode D, and the capacitor Cst is charged.